1. Field of the Invention
The invention is in the field of brake hose support systems for railway cars, and in particular, the invention is directed to a novel hose strap, adapted to engage with American Association of Railroads (“AAR”) standard coupler heads and brake hose fittings.
2. Description of Related Art
In a railway car coupler system, a supporting device is used for suspending the glad hand of an air brake hose assembly from the couplers of railway vehicles. AAR standards specify a minimum distance between the ground and the glad hand fitting, so that the straps are made adjustable between a length of 16 inches and 22 inches. Conventionally, the supporting device, also called an air brake hose support or hose strap, was a metal chain whereby, one end of the chain could be connected to a fitting on the glad hand on the free end of the air hose and the other end could be connected to a fitting on the coupler of the railway vehicle.
When a glad hand fitting becomes decoupled, especially if the appropriate valves are not shut off, compressed air in the hose propels the glad hand, which in turn exerts a load on the strap, referred to herein as “reaction force.” A chain support does not absorb this energy when the glad hand fitting is decoupled, causing increased reaction force. As a result, the full energy from the decoupling is delivered to the impact when the glad hand fitting strikes the car or other machinery. The chain and connectors are also susceptible to breakage, which can lead to the air hose being pulled along the trackway, or to the glad hand being caught in wayside equipment resulting in damage to the air brake hose assembly.
Rubber air brake hose supports are also known in the prior art which absorb energy generated from hose separations better than metal chain air brake hose supports. A rubber strap stretches to absorb energy, thereby reducing the reaction force when hoses are decoupled. A rubber air brake hose support exhibits much less reaction force as compared to a metal chain under the same hose separation conditions.
Some examples of flexible air brake hose supports are shown and disclosed in U.S. Pat. No. 3,592,425, U.S. Pat. No. 3,784,030, and U.S. Pat. No. 4,986,500. These air brake hose supports have a flexible strap having a plurality of holes with a fastening system at each end thereof including metal clips. The clips can be moved to engage different holes on the strap to adjust the length.
It has been found, however, with the current designs of rubber hose straps, that failure often originates where the metal clips meet the holes in the flexible member. Where clips have been provided having two legs in adjacent holes on the strap, the holes on the flexible member have been spaced so that only the leg closer to the load bears significant load during use, and the leg farther from the load is prone to pulling out of the hole when load is applied. When a second leg pulls out of the hole, or if the air brake hose support has only one leg on the clip threaded though the flexible strap to begin with, the clip can rotate and cause lateral loading, which is another common cause of failure.
While the prior art air brake hose supports function satisfactorily under normal conditions, there are still problems with reaction force and load support. These field problems have caused the Association of American Railroads (AAR) to adopt a new standard, S-4006, effective Nov. 1, 2009.
The present invention is directed to an improved hose strap having a flexible strap and associated clips, which addresses the problems long recognized in the prior art, while meeting or exceeding the new AAR standards.